Your PDB file must be using some old atom names. makeDIST_RST uses the
information in the $AMBERHOME/dat/map.DG-AMBER file, so you can look there.
The PDB standard now uses H2' and H2'' as atom names for deoxy sugar hydrogen
atoms, not H2'1, H2'2. You need to either change your pdb file or the map
file; the former is probably better.